Electronic device



Nov. 5, 1940- K w. JARVIS ETAL ELECTRONIC DEVICE 2 Sheets-Sheet 1 FiledDec. 24, 1936 VOLTAGE BY 3% r ATTORNE K. w. JARVIS ETAL 2,220,452

' ELECTRONIC DEVICE Filed Dec. 24, 1956 2 Sheets-Sheet 2 i l l l l -ll"U I CUfiRfA/T VOLT AGE Nov. 5, 1940 UNITED STATES PATENT OFFICEEmc'raomc DEVICE Kenneth W. Jarvis, Silvermine Falls, Norwalk, andRussell M. Blair, Westport, Conn., assignors to Radio Corporation ofAmerica, New York. N. Y., a corporation of Delaware Application December24, 1936, Serial No. 117,660

18 Claims. (Cl. 179-1715) The present invention relates to oscillationcircuits and in particular to circuit arrangements adapted for use inconnection with the operation of secondary emission electron and vacuumtubes of the general types described in our U. S. Patent No. 1,903,569issued April 11, 1933 to Russell M. Blair and Kenneth W. Jarvis, and forwhich a reissue application Serial No. 16,108 has been filed, on April8, 1935. This has matured into Reissue Patent No. 20,545 grantedNovember 2, 1937.

In the conventional grid-controlled thermionic amplifier, amplifyingaction is obtained by virtue of the grid or control electrode beingspaced closer to the electron emitter than the anode or outputelectrodes, and the ratio of amplification is to a first degree ofapproximation equal to the ratio of the electrostatic fields set upbetween the emitter-grid and the emitter-anode. Since theseelectrostatic fields depend almost solely upon the geometricconfigurations of the various electrodes, the amplifying characteristicof the tube, in turn, is determined by the size and positioning of. theelectrodes. By suitable energy feedback such amplifiers can be made tooscillate.

In contra-distinction, our invention provides an amplifying system whosegain characteristic is not so dependent but is dependent upon sec-'ondary emission effect. The amplifying characteristic which we provideis largely fixed by the ratio of secondary electron emission to'theprimary electrons initiating the emission of the secondary electrons. Bysuitably feeding back energy to a control circuit, oscillations can-begenerated and sustained.

A further feature of our invention lies in the manner of producing anegative resistance characteristic which can be combined with a suitableelectrical network to generate and maintain oscillations. In previoustypes of secondary emission discharge devices, negative resistanceoccurs because the secondary emission current leaving a referenceelectrode is greater than the primary emission current reaching theelectrode. Secondary emission from the reference electrode is anecessity for operation. In our invention, however, the negativeresistance characteristic is obtained in an entirely new and novelmanner, as there is no' secondary emission from the reference electrode.The negative resistance characteristic is derived from a decrease inoutput current, due to a decrease in secondary emission augmentation ofthe output current, as the output voltage is increased. This effect isdifferent from previous types of oscillators and,

has many useful advantages that result from the isolation of thesecondary electrons emitted from the primary stream of electrons.

- Thus our invention relates to the use of primary and secondaryelectron streams and asso- 5 ciated tube and circuit elements andoperating potentials for producing systems capable of oscillation. It isan object of this invention to provide a means for converting directpotentials into alternating potentials covering the extreme range 10 offrequencies.

A still further object of this invention is to provide a new andimproved type of-oscillator, substantially difierent from known previoustypes. 16

Still another and further object is-to provide for a new type ofnegative resistance oscillator, wherein the negative resistance isobtained in an entirely new and novel manner.

Turning now to the drawings, in which Fig. 1 20 shows the circuit of anew type of oscillator,

Fig. 2 shows graphically the current-voltage relationship of tubes usedin our invention as an aid in explaining the operation of Fig. 1-,

Fig. 3 is another embodiment of our invention 25 showing a method formodulating the =type.of oscillator shown in Fig. 1;

Fig. 4 is another current chart of output voltage against output currentof a negative resistance characteristic,- and Fig. 5 shows an embodimentof our invention having a characteristic shown in Fig. 4; our inventionwill be described in detail.

- Fig. 1 shows our new oscillator arrangement made possible by theeffective power amplifica- 5 tion released through the phenomena ofsecondary emission. The tube structure I includes an emitter 2, acollector plate 3 adapted for the emission of secondary emission on theimpact of primary emission, an output plate 4 and a shield- 0 ingelement 5. The source of potential 6 activates the emitter 2, while thesource of potential I maintains the collector plate 3 at the properaverage potential. As here shown, the source of potential 8 is added tothat of I to furnish plate 45 supply for the output plate 4. Separatepotentials can be used if preferred, or any other dual potentialarrangement, if desired. The source of potential 9 is used to polarizethe shielding element 5. The primary charge stream is indicated 50 atl0, and the resulting secondary charge stream at H. The electricalnetwork connected to the output plate 4 includes the inductance l2connected in parallel with the condenser l3. The inductance I4 iselectromagneticaliy coupled to 55 the inductance I 2, and is connectedin the external circuit between the collector plate 3 and the emitter 2.

In order to explain the resulting action, attention is directed to Fig.2. Here is shown the magnitudes of the currents I10 and In with respectto voltage E1 in Fig. 1. Starting from zero current I10 increases to asaturation value as indicated by the upper bend of the characteristiccurve. The current In is substantially directly proportional to 110, theproportionality factor .being the secondary emission ratio. This ratiovaries near the extremes of the curves but this variation is very smallwhen the tube is operated over the linear portion of the characteristic.It is obvious that a small change in voltage E1 will produce a smallchange in I10 and a very large change in In in the linear regions ofcurrent voltage, but that in the saturation region, no substantialchange takes place.

In the circuit of Fig. 1, the ratio of the secondary emission current tothe primary electron current is utilized to make the device act as apower amplifier, and so under proper conditions, to oscillate. As thistype of oscillator is essentially new in action, a rather detaileddescription is necessary. Assume that the total poten tial between theemitter 2 and the collector plate 3 is increasing. This will increasethe currents I10 and I11. The current In flowing through the inductancei 2 will induce a voltage in the in-,

ductance I. If the proper polarity of connections is observed, thisinduced voltage will add to that of the source of potential I. Thisaddition raises the total potential between the emitter 2 and thecollector plate 3, which in turn increases the currents. If the suppliedpotential is suitably chosen, this action is cumulative and the currentIn builds up to substantially the saturation value. At thispoint,increasing the total control potential will not increase In andtherefore the induced potential in the inductance it disappears. Thetotal control potential is therefore only that due to the source E1 andis not sufiicient to maintain I11 at saturation value. In thereforedecreases, and in so doing introduces in the inductance II a potentialof opposite sign to the source E7. This reduces the net control voltageto a value still lower than the source E1, and the current In continuesto fall. After reaching substantially zero In cannot decrease furtherand therefore the induced negative voltage in the inductance againbecomes zero. The net control potential now approaches that of thesource E1, the current In increases, the induced voltage in theinductance H adds to that of the source E1 and the cycle repeats itself.In view of the high secondary emission ratio possible, provided by theconditioning of the col-' lector plate 3, far more power is liberated bythe output plate circuit than is required to maintain the needed controlpotentials. Accordingly, useful power may be obtained from the outputcurrent without stopping the oscillation.

It is important to note that' while the effective resistance lookinginto the control plate I circuit is negative, that this negativeresistance effect is unimportant except that it is one of the neces-'sary accompanying conditions under which power is released by secondaryemission. If the resistance loss at high frequencies be increased in theexternal circuit of a conventional negative resistance dynatron to avalue greater than the negative resistance will nullify, the dynatronwill stop oscillating. On the contrary, in our inventransformer 23connected in series with a polariztion, if such losses be introducedinto the external collector plate ifclrcuit of Fig. 1, the circuit willnot stop oscillating since these losses can be supplied by the outputplate 4 circuit of Fig. 1. In general, with the secondary emission 5ratio now obtainable, this is easily accomplished. The circuitarrangement is therefore totally unlike the conventional dynatron-typeof oscillator. The circuit of Fig. 3 shows a widely useful adaptation ofthe type of-oscillator described in Fig. 1. The oscillator of Fig. 3 issubstantially like that of Fig. 1, but certain additions are to benoted. In Fig. 3 the prime numbers indicate those elements which performsimilar functions to the functions of the elements in Fig. l. The tubestructure is denoted by l5, while the emitter I6 is heated by thebattery I 9. A control grid I1 is interposed between the emitter l6 andthe first collector plate 2'. As this collector plate 2' also serves asthe source of emission for the rest of the tube which acts as theoscillator, the old number 2' is retained. The shield I8 and source ofpotential 2| is shown, as well as an input ing potential 20. The battery22 supplies poten- 25 tial for the collector plate 2'. As the amplitudeof oscillation is largely dependent on the emission from the collectorplate-2', so is it also dependent on the primary emission 24. This inturn is controlled by the potential on the grid l1, and so modulationpotentials impressed on the grid I'I serve to control the amplitude ofoscillation. This combination therefore serves very well as a modulatedoscillator. One important advantage of this type of modulated oscillatorover other types is that no translating impedances need be includedbetween the modulation frequency source (grid l1) and the succeedingoscillator. It can thus be modulated by D. C. or potentials of anyfrequency alike. Accordingly, the modulation of the oscillations doesnot introduce any frequency distortion or phase-shift of the modulatingpotentials. This feature is of the greatest importance where the bandwidth of frequencies of the modulating potentials is great, as forexample, in television transmission. In such transmissions, the videosignal band-width is on the order of millions of cycles and it has beenpractically impossible to avoid frequency discrimination and phase shiftof the modulating potentials. To overcome this deleterious feature,complicated correction networks are employed which in general reduce theoverall efllciency of the system. Our invention overcomes thesedeleterious effects without resorting to complicated networks so that afurther improvement in efllciency results.

It should also be noted that instead of a constant emission source andvariable grid control, that a variable source of emission such as in aphototube may be similarly directed against the collector plate 2' andserve to modulate the oscillator portion.

The elimination of the translating or coupling impedance permitssubstantially uniform modulation of the entire frequency band, a featurelacking in modulator-oscillator systems of the ages are assumed to be atsuitable operating values. This curve shows that while secondaryelectrons are emitted out of theplate II. Fig. 5, they will not go tothe output plate 32 until the output potential E36 is greater than thecollector plate potential E35. Beyond this point, In increases, 14remaining constant. This point of increase in current is shown in Fig. 4at the point 25. Due to the constant primary current 140, the secondaryemission current I41 can be no greater than this primary current timesthe secondary emission ratio at the collector plate 3|. limit is reachedabout the potential indicated at 42, Fig. 4. As the potential E38 isfurther increased, changes in the electrostatic field occur, but due tostructural design little change in current I41 takes place until thepoint 26 is reached. At this point, the high potential E35 acts aroundthe edge of the shielding element 33 and begins to draw the primaryemission directly to the output plate 32 without producing secondaryemission. As a result, the ratio between primary and secondary electronsis reduced, and the output plate current In decreases. This decreasecontinues to the point 28 where all the primary emission is drawn aroundand no secondary emission increase is present. If the emission from theemitter 35 is saturated, the final current I41 will equal I40 for allsubsequent increases in E36. If not saturated, 141 will "gradually climbbeyond the point 28 to the saturation current. The curve between thepoints 26 and 28 exhibits a negative resistance characteristic. This maybe used as any other negative resistance, and in conjunction with atuned circuit of equal positive resistance, will oscillate. Such a tunedcircuit is included in the output plate 32 circuit of Fig. as theinductance 38 and tuning condenser 39. For normal operation thepotential E38 is adjustedto a point on the linear portion of thenegative slope of the voltage current characteristic, as for examplepoint 21 of Fig. 4, which is about centered in the negative resistanceregion. The circuit and system will then oscillate, the potentialswinging approximately between the points 25 and 28. The oscillationcycle of our invention is substantially that followed by so-callednegative resistance discharges, and since these are well known in theart, it' is believed to be unnecessary to discuss them further at thispoint.

Other changes and modifications may suggest themselves to those skilledin the art without departing from the scope and spirit of our invention.

What we claim is: l

1. The method of operating an electronic device wherein is provided asecondary electron emissive electrode comprising the steps of producinga supply of primary electrons, producing a constant electronaccelerating field between the produced supply of electrons and theemissive electrode to direct the primary electrons thereon, emittingsecondary electrons from the emissive electrode under the control of theprimary electrons arriving on the emissive electrode, segregating theemitted secondary electrons from the primary electrons, collecting thesegregated secondary electrons, and varying the produced acceleratingfield only in proportion to the variation in the number of electronscollected per unit of time.

2. An electronic device comprising a'secondary electron emissiveelectrode, means for producing a supply of primary electrons, means forproducing a constant electron accelerating field between the electronproducing means and the emissive electrode to direct the primaryelectrons thereon, means for emitting secondary electrons from theemissive electrode under the control of the primary electrons arrivingat said electrode, means for segregating the emitted secondary electronsfrom the primary electrons, means for collecting the segregatedsecondary electrons, and means for varying the produced acceleratingfield in proportion to only the variation of the number of electronscollected per unit of time.

3. An electronic device comprising a source of primary electrons, asecondary electron emissive electrode, means for electrostaticallydirecting primary electrons at a constant rate toward said electrode toimpact thereon and feedback means between the source of primaryelectrons and the secondary electron emissive electrode for varying theemission of secondary electrons from the said electrode from zero tosubstantially saturation value under the control of primary electrons.

4. An electronic device comprising a source of primary electrons, atsecondary electron emissive electrode, means for electrostaticallydirecting primary electrons at a constant rate toward said electrode toimpact thereon ,and feedback means between the source of primaryelectrons and the secondary electron emissive electrode for cyclicallyand periodically varying the emission of secondary electrons from thesaid electrode from zero to substantially saturation value and back tozero under the control of primary electrons.

5. The method of operating an electronic device which comprises thesteps of producing a stream of primary electrons, accelerating theproduced stream of electrons toward a secondary electron emissivesurface at a constant rate, releasing secondary electrons from saidemissive surface under the direct control of the number of acceleratedelectrons .arriving at said emissive surface, segregating the releasedsecondary electrons from the accelerating electrons, collecting thesegregated secondary electrons, and producing a potential differencebetween the source of primary electrons and said emissive surface onlyin proportion to the variation of the number of secondary electronscollected per unit of time, whereby the ratio of released secondaryelectrons to primary electrons arriving at the emissive surface isvaried.

6. In an electronic device wherein is provided a source of primaryelectrons and an electrode for emitting secondary electrons under theimpact of primary electrons, the method of operating which includes thesteps of electrostatical- 1y only accelerating primary electrons fromthe source to said electrode at a constant rate and varying the ratio ofsecondary electrons emitted per unit of time to the primary electronsimpacting the said electrode per unit of time from zero up to apredetermined maximum value.

7. In an electronic device wherein is provided a source of primaryelectrons and an electrode for emitting secondary electrons under theimpact of primary electrons, the method of operating which includes thesteps of electrostatically only accelerating the primary electrons fromthe source to said electrode at a constant rate, and cyclically andperiodically varying the ratio of the secondary electrons emitted perunit of time to the primary electrons impacting said electrode per unitof time from zero up to a predetermined maximum value and back to zero.

8. The method of operating an electronic device which comprises thesteps of producing a stream of primary electrons, accelerating 'theproduced stream of electrons toward a secondary emissive surface at aconstant rate, releasing secondary electrons from said emissivesurfaceunder the direct control of the number of accelerated electrons arrivingat said emissive surface, segregating the released secondary electronsfrom the accelerated electrons, collecting the segregated secondaryelectrons and producing a potential difference between the source ofprimary electrons and said emissive surface only in proportion toincreases and decreases of the number of secondary electrons collectedper unit of time, whereby the ratio of the released secondary electronsper unit of time to the primary electrons arriving at the emissivesurface per unit of time is varied.

9. The method of operating an electronic device wherein is provided asecondary electron emissive electrode comprising the steps of producinga supply of primary electrons, producing a constant electronaccelerating field between the produced supply of electrons and theemissive electrode to direct the primary electrons thereon, emittingsecondary electrons from the emissive electrode under the direct controlof the primary electrons arriving at said electrode, segregating theemitted secondary electrons from the primary electrons, collecting thesegregated secondary electrons, and varying the produced acceleratingfield only in proportion to increases and decreases of the number ofelectrons collected per unit of time, whereby the ratio of the releasedsecondary electrons per unit of time to the primary electrons arrivingat the emissive surface per unit of time is varied.

10. The method of operating an electronic device comprising the steps ofproducing a stream of primary electrons, electrostatically onlyaccelerating the produced stream of electrons to ward a secondaryelectron emissive surface at a constant rate, releasing secondaryelectrons from said emissive surface under the direct control of thenumber of accelerated electrons arriving at said surface, segregatingthe released secondary electrons from the accelerated electrons, varyingthe ratio of the released secondary electrons per unit of time toprimary electrons arriving at said surface per unit of time from zerojup to a predetermined saturation value,-and collecting the segreatedsecondary electrons.

11. The method of operating an electronic device comprising the steps ofproducing a stream of primary electrons, electrostatically onlyaccelerating the produced stream of electrons toward a secondaryelectron emissive surface at a constant rate, releasing secondaryelectrons from said emissive surface under the direct control of thenumber of accelerated electrons arriving at said surface segregating thereleased secondary electrons from the accelerated electrons, cyclicallyand periodically varying the ratio of the released secondary electronsper unit of time to the primary electrons arriving at said surface perunit of time from zero to a predetermined saturation value and back tozero, and collecting the segregated electrons.

12. The method of operating an electronic device comprising the steps ofproducing a stream of primary electrons, electrostatically onlyaccelerating the produced stream of electrons toward a secondaryelectron emissive surface at a constant rate, releasing secondaryelectrons from said emissive surface under the direct control of thenumber of accelerated electrons arriving at said surface, segregatingthe released secondary electrons from the accelerated electrons,collecting the segregated secondary electrons, producing a'potentialdifference between the source of primary electrons and said emissivesurface only in proportion to the variation of the number of secondaryelectrons collected per unit of time, and varying the number ofsecondary electrons from zero to a predetermined saturation value underthe control of the produced potential difference.

13. The method of operating an electronic device comprising the steps ofproducing a/stream of primary electrons, electrostatically onlyaccelerating the produced stream of electrons toward a secondaryelectron emissive surface at a constant rate, releasing secondaryelectronsfrom said emissive surface under the direct control of thenumber of accelerated electrons arriving at said surface, segregatingthe released secondary electrons from the accelerated electrons,collecting the segregated secondary electrons, producing a potentialdifference between the source of primary electrons and said emissivesurface only in proportion to the variation of the number. of secondaryelectrons-.collected per unit of time, and cyclically andperiodicallyvarying the number of secondary electrons from zero to a predeterminedsaturation value and back to zero.

14. In anelectronic device wherein is provided a secondary electronemissive electrode, the method of operation which comprises the steps ofproducing a stream of primary electrons, electrostatically onlydirecting the produced stream of electrons toward the emissive electrodeat a constant rate, bombarding the emissive electrode by the directedstream of electrons to produce secondary electrons, segregating theproduced secondary electrons from the primary electrons, continuouslycollecting the segregated secondary electrons, and periodically only'atpredetermined time intervals, collecting primary electrons directly fromthe produced stream in addition to the secondary electrons.

15. An electronic device comprising means for producing a stream ofprimary ele'ctrons, means for accelerating the produced stream ofelectrons toward a secondary electron emissive surface at a constantrate, means for releasing secondary electrons from said emissive surfaceunder the direct control of the number of accelerated electrons reachingsaid surface, means for segregating the released secondary electronsfrom the accelerated electrons, means for collecting the segregatedsecondary electrons, and means for producing a potential differencebetween the source of the primary electrons and said emissive surface inproportion to only the variation in the number of secondary electronscollected per unit of time whereby the ratio of the secondary electronsreleased per unit of time to accelerated electrons reaching said surfaceper unit of time is varied.

16. In an electronic device a secondary emissive electrode, means forproducing a streanrof primary electrons having constant accelerationmeans for only electrostatically bombarding the emissive electrode bythe produced stream of electrons to produce secondary electrons, meansfor segregating the produced secondary electrons from the primaryelectrons, means for continuously collecting the segregated secondaryelectrons, and means for only periodically at predetermined timeintervals'collecting primary elem trons directly from the producedstream in addition to the secondary electrons.

17. The method of operating an electronic device which comprises thesteps of producing a stream of primary electrons, producing a constantelectron accelerating field to direct the primary electrons toward asecondary emissive surface, releasing secondary electrons from saidemissive surface under the direct control of the number of acceleratedelectrons arriving at said surface, segregating the released secondaryelectrons from the accelerated electrons, and superimposing upon theproduced field another accelerating field whose value is in proportionto only the variation of the number of electrons collected per unit oftime.

18. In an electronic device, means for producing a stream of primaryelectrons, means for producing a constant electron accelerating field todirect the primary electrons toward a secondary emissive surface, meansfor releasing secondary electrons from said emissive surface under thedirect control of the number of accelerated electrons arriving at saidsurface, means for segregating the released secondary electrons from theaccelerated electrons, and means for superimposing upon the producedfield another accelerating field whosev value is in proportion to onlythe variation of the number of electrons ,collected per unit of time.

KENNETH W. .TARVIS. RUSSEEL M. BLAIR.

